Liquid compositions, particularly aqueous detergent compositions comprising appreciable amounts of surfactants may be difficult to formulate, given their tendency to split into two or more phases, such as one or more surfactant-rich phases and a water-rich phase. Further technical difficulties may arise when particulate matter is to be suspended in surfactant-containing liquid compositions as the particulates may have a tendency to rise to the top or to settle to the bottom of the composition over time. Yet consumers delight in fluid detergents offering stabilized particulate materials which can deliver cleaning performance, fabric care benefits, appearance benefits, and/or visual or aesthetic cues. Full internal structuring through reliance upon the intrinsic structuring properties of highly concentrated surfactants is one approach that may be utilized to stabilize dispersed particulate materials. However, this approach may waste surfactant and can limit formulation flexibility. These and other associated technical difficulties may be overcome while maintaining consumer delight through the use of external structurants and systems comprising them.
Aqueous laundry detergent compositions which are stabilized through the use of external structuring system(s) (ESS) comprising hydroxyl-containing stabilizers have been described. Hydrogenated castor oil (HCO) is a non-limiting example of a useful hydroxyl-containing stabilizer. HCO may be formulated into laundry detergent compositions using sodium-neutralized linear alkylbenzenesulfonate (NaLAS), a common laundry detergent anionic surfactant. It is believed that NaLAS acts as an emulsifier for the HCO structuring system. The acid form of LAS (HLAS) for use in such systems may be neutralized for example, with sodium hydroxide to form NaLAS. The structurant system may be prepared by forming, separately from the balance of the detergent composition, a melt of HCO in aqueous Na-neutralized LAS, which may then be stirred to form an emulsion of molten HCO. This emulsion may then be cooled to crystallize the HCO. Upon crystallization, an external structurant in the form of a premix may be yielded. The premix may then be added to the balance of a liquid laundry detergent composition in order to structure it. Alternatively, the structurant may be crystallized in-situ by mixing the molten emulsified HCO premix with the balance of the detergent composition and then cooling.
Liquid detergents, particularly liquid detergents with low water content, and detergents in gel form, may be desirable since they can be more sustainable than their more dilute counterparts. It has now been discovered that it may be undesirable to introduce inorganic ions such as alkali metal ions or more particularly Na-ions, into external structuring systems used to prepare liquid or gel-form surfactant-rich detergents having relatively low water and/or solvent content.
It has further, rather surprisingly been discovered that, even though the total amount of sodium introduced into a liquid or gel-form laundry detergent via an ESS is not large, e.g., up to about 4% by weight, changing the HCO emulsifier from a sodium-neutralized anionic surfactant form to an alkanolamine neutralized anionic surfactant form, especially a monoethanolamine (MEA) neutralized LAS form improves the visual appearance and/or phase stability and/or particulate matter carrying capacity, as measured by conventional rheology techniques, of both of the external structurant mix and of the finished liquid or gel-form laundry detergent.